Browsing by Subject "emulsion"

The objective of the thesis was to investigate the effect of carbohydrates on solubility, emulsifying, gelling and water holding properties of proteins. Faba bean is a readily available pulse crop with high protein content similar to soy bean and there is a lot of potential for a novel, high protein fermented gel product to be made from a pulse crop like faba bean. This is mainly due to its remarkable nutritional properties, functional properties and low cost, the demand for faba bean protein ingredients will grow. The current study was an attempt to develop pulse protein based products – emulsion (milk-like) and emulsion gel (yogurt-like) from faba bean. It seeks to expand the field of application of faba bean protein based products. Faba bean was pretreated, dehulled and milled. The flour was made into suspensions and the starch in faba bean was subjected to amylolytic treatments (addition of alpha amylase and glucoamylase) to breakdown the starch into smaller particles. These treated suspensions were then homogenized to obtain emulsion. A protein based gel network was produced with the gelation of amylolytically treated faba bean proteins. The emulsion properties, specifically droplet size, stability and activity were tested by PAMAS Particle Counter System. Light microscopy was applied to reveal the microstructure of emulsion and emulsion gel. Emulsion gel texture properties were studied by texture analysis. The emulsions were relatively stable over a period of a month and had white ‘milk’ like appearance. The emulsion gels prepared (amylolytic treatment) had slightly higher water holding capacities than the control A (entire starch present) and control B (starch removed by filtration) emulsion gels. Texture analysis of the emulsion gels showed that more force was required by probe to penetrate the yogurt produced from amylolytically treated samples and less force was required to penetrate the yogurt produced from controls A and B. The yield of the emulsion gels were higher for the amylolytically treated samples. It can be concluded that amylolytic treatment has increased the water holding capacity and also resulted in stronger gel systems.

Infant formulas are breast milk substitutes for 0 to 12-month-old infants. Addition of milk fat to infant formulas leads to an increase in solid fat content. Infant formulas are oil-in- water emulsions in which oil is dispersed into a continuous aqueous phase. Milk fat crystallization leads to partial coalescence and creaming which are types of instability in emulsions. Partial coalescence occurs when two droplets containing crystals collide and they partially coalesce by making contact between their oil phases. The aim of this thesis was to study if milk fat crystallization leads to partial coalescence which leads to a higher rate of creaming or the increasing density of crystallizing droplets leads to a lower rate of creaming. Also, the aim was to study the effect of interfacial layer on partial coalescence. Milk fat crystallization and emulsion stability were investigated from four series of oil-in- water emulsions containing different oils in different concentrations and either whey protein or lecithin as stabilizer. The samples were stored at 5, 20 and 40 °C and measured after 0, 7 and 28 days of storage. The crystallization of bulk fat and oil in emulsions were studied with melting enthalpies measured with differential scanning calorimetry. Emulsion stability was examined with particle size distribution, instability index and creaming velocity measurements. According to the results combining vegetable oil and butter oil, and emulsifying the fat decreases the total enthalpy change and crystallization onset temperature of oils. Mixing vegetable oil and butter oil before homogenization decreased crystallization onset temperature and total enthalpy change because the oils were in same droplet, and made the emulsions behave more like vegetable oil emulsions. Mixing the oils after homogenization made the emulsions behave similarly to butter oil emulsions. Whey protein was found to be a better stabilizer of emulsions than lecithin at 5 and 20 °C, but at 40 °C some Maillard reaction was noticed. It was suspected that the concentration of lecithin in emulsions was insufficient. Based on the results it could be stated that the increasing density due to crystallizing droplets made the emulsions more stable against creaming. Best stability of emulsions containing oil mixtures would be achieved if butter oil and vegetable oil were mixed after homogenization and whey protein used as emulsifier.

The literature review detailed the theoretical background for this study, identified the possibility about development of faba bean protein stabilized emulsion for food products and studied the effect of increased oil addition on the structure of emulsions. The practical work was divided into three parts emulsion analysis, emulsion gel analysis and sensory evaluation. Various research methods were applie d to support this study, including droplet size distribution , droplet charge ζ potential), texture evaluation, and rheological analysis. This study showed that oil addition increased emulsion droplet size, as well as the absolute value of ζ potential . Emulsifying activity index (EAI) and emulsion stability index (ESI) decreased with increasing oil concentration. F aba protein stabilized emulsions were better stabilized by oil addition , compared with those without oil additi on . From texture analysis of gel properties, firmness improved with increasing oil concentrations (0% 30%). In addition, rheolog ical analysis for faba yogurt samples showed that increasing oil concentrations improved the viscosity of the faba yogurt samples. T he results also illustrated that increasing oil concentrations led to increased deformation meaning the emulsion gels were more easily destroyed with increasing oil concentrations (0 30%). Oil addition resulted in higher whiteness when compared with samples without oil. Sensory evaluation by a professional panel for faba yogurt samples indicated that samples with 20% oil concentration w ere the most preferred and had the highest overall quality .

The scope of the literature review was to define the process for oil-in-water emulsion formation and the important properties of the emulsions which are suitable for microencapsulation. The aim of this study was to determine how whey protein isolate together with maltodextrin affects the properties of the emulsion. Camelina oil and black currant seed oil were used as core materials. The wall materials used were: maltodextrin (MD) and whey protein isolate (WPI). Six different wall systems consisting WPI in combination with MD at various ratios (1:1, 1:3 and 1:9) were used. In premilinary tests the emulsions were characterized for temperature, creaming index, apparent viscosity, flow behavior index, flow consistency index, droplet size (D4,3 zetasize,), droplet size distribution (PDI, span) and zetapotential. Droplet size and droplet size distributions were measured by a laser light scattering using a Zetasizer and by laser light diffraction instrument, Mastersizer 2000/3000. Oil droplet size was also measured with light blockade using a PAMAS. Rheological properties were characterized with rheometer. In actual test the emulsions were characterized for time (foam removal), temperature, droplet size (D10, D50, D90 ja D4,3), apparent viscosity, flow behavior index and flow consistency index. First degree polynomial was fitted with PLSR to the results. Statistical significances of regression coefficients were analyzed with t-test. In premilinary tests all the emulsions were stable during storage at 25 °C after 24 h. pH and zetapotentials which were all lower than -35 mV refer to good stability of emulsions. Change in droplet size and droplet size distribution was observed. Increasing maltodextrin concentration decreased droplet size (D4,3) and droplet size distribution width (PDI) when measuring by Mastersizer and Zetasizer. Apparent viscosity of the emulsions decreased by increasing maltodextrin concentration. PLS-regression showed that there were statistically differences between wall materials and temperatures, droplet size, size distribution and apparent viscosity. There were also statistically differences between oil and droplet size measured by PAMAS. In actual tests apparent viscosity of the emulsions decreased by increasing maltodextrin concentration. Increasing maltodextrin concentration also decreased the time of foam removal. PLS-regression showed that there were statistically differences between wall materials and temperatures after homogenization, time (foam removal), flow consistency index and apparent viscosity. There were also statistically differences between oil and temperatures, flow behavior index and droplet size distribution width. Whey protein isolate together with maltodextrin affect mostly to apparent viscosity of emulsions.

Oat beta-glucan, β-glucan, is a soluble dietary fibre located in the endosperm and aleurone cell walls. It is a polysaccharide that has an ability to form viscous gel in aqueous solutions due to its high water binding capacity. The objective of this study was to determine the physical characteristics of commercial oat β-glucan with different purity in solution. Four commercial oat beta-glucan powders with varying β-glucan content were provided for this study. Solubility, water binding capacity, viscosity, suspension and emulsion stability, droplet particle size, particle distribution and zeta potential were determined from the samples. There were two phases in the experimentation part in which the first phase focused on suspensions and the second phase focused on emulsions. There were four different homogenising treatments used to solubilize the samples into water during the first phase of the experiment, which were stirring in room temperature, 80 ˚C, Ultra-Turrax and microfluidization. Megazyme exhibited highest solubility in water with a solubility rate of 100 % regardless of the treatment used. OatWell had the highest water binding capacity (11.7 g/g) after heat treatment. Heat treated OatWell had the highest viscosity (590 mPas). Megazyme emulsions had the highest emulsion stability (TSI ranging from 0.6 to 3.6) as it did not experience phase separation until fifth day of measurement. Megazyme emulsions also had the lowest particle sizes ranging from 0.4 μm to 1.5 μm. The results of this study highlight that the content of β-glucan has notable effect on its solubility and the homogenisation treatment used has an increasing effect on solubility and decreasing effect on water binding capacity and viscosity. Purity of the oat β-glucan also has an effect on emulsion stability as high purity oat β-glucan are able to stabilise emulsion system after homogenisation.

Finding new plant-based protein sources is important from a sustainable development perspective. Ethanol and starch production from barley results in fiber and protein side-stream fractions that are currently utilized for animal feed. Nonetheless, it would be more profitable if the barley protein side-stream was used as a human food ingredient. The main storage proteins in barley are known as hordeins. They are polymeric proteins and have low solubility, due to their inter-chain and inter-molecular disulfide bridges and hydrophobic side-chains. In food technology applications protein solubility is an important property for emulsifying and foaming functionality. Proteins are sensitive to the surrounding environment, especially to pH, which could be used to alter the solubility. In this thesis the literature review examined barley (Hordeum vulgare) proteins, especially the hordeins, functionality and effect on food materials. The review includes previous studies concerning cereal proteins functionality in general and their effect on food materials and a discussion on protein stabilized emulsions. The aim of the study was to determine the protein composition of two barley protein concentrates, OP1 and OP2, and to evaluate protein solubility and emulsifying properties. Furthermore, the aim of the study was to compare the functionality of the concentrates. According to SDS gel electrophoresis the protein concentrates consisted mostly of hordeins, especially C-hordein and some B-hordein. Minor amounts of other proteins where also identified. The protein solubility was determined by Lowry’s method. The proteins were more soluble in sodium phosphate buffer than in deionized water. In sodium phosphate buffer at pH 3,8 the solubility of OP1 proteins was 100 mg/g ± 11 mg/g and in deionized water at pH 3,9 the solubility was 45 mg/g ± 1,1 mg/g. The solubility of the OP2 proteins in sodium phosphate buffer at pH 3,8 was 47 mg/g ± 1,5 mg/g and in deionized water at pH 3,7 the solubility was 45 mg/g ± 1,1 mg/g. In both samples the proteins solubility increased as the pH increased. Most proteins were solubilized at pH 11: the solubility for OP1 and OP2 proteins were 240 mg/g ± 11 mg/g and 140 mg/g ± 12 mg/g respectively, which is problematic regarding food products, but could be used as a treatment to improve solubility. The smallest oil droplets were formed in emulsions were the pH was adjusted to 7 with sodium phosphate buffer. The stability of emulsions was however poor in all samples because of phase separation, which was already significant after one day of storage. The phase separation was considered to be flocculation which finally resulted in creaming or sedimentation. The flocculation may have occurred due to hydrophobic interactions between the proteins on the oil/water interface. However, shaking of the emulsion causes the flocculated oil droplets to separate, forming an even emulsion. No coalescence was observed in all samples, except for OP1-emulsions with 1 % (w/v) dry matter. These results confirm that these protein concentrates can be used in food products, especially in milk type drinks that need to be shaken before usage.

Norway spruce (Picea abies) and silver birch (Betula pendula) are widely spread in Europe. They are important raw materials for sawmill, pulp mill and paper industry. This industry utilizes merely 30-40% of the wood in the form of cellulose. Hemicelluloses, mainly galactoglucomannans (GGM) in spruce and glucuronoxylan (GX) in birch, comprise around 30% of the mass of wood. By far, this part has not been utilized as raw material but burnt as a source of energy. GGM and GX can be recovered from sawmills, paper making and pulping process, according to current knowledge, utilized as emulsion stabilizers. This study aims at evaluating the role of wood extractives present in hemicellulose isolates for emulsion stabilization. This study investigated the characterisation of wood extractives in isolated hemicelluloses and evaluated the role of wood extractives in stabilization of hemicelluloses emulsions during lipid oxidation. In the experimental section, eight different spruce galactoglucomannan (GGM) isolates and two birch glucuronoxylan (GX) isolates were characterized for their wood extractive composition and their antioxidant capacities were evaluated. The isolates were collected from thermomechanical pulping (TMP), by pressurized hot-water extraction (PHWE) or by mild alkali pressurized hot-water extraction (BLN). The isolates were either used as such (Con), after spray-drying (Spdr) or after ethanol precipitation (EtOH). The content and composition of phenolic residues and triterpenes in hemicellulose isolates were determined and their effect on the emulsion stability were investigated. In addition, radical scavenging activities and metal binding capacity were investigated to further understand the role of wood extractives against lipid oxidation in emulsions. Lipid oxidation in emulsions were investigated by monitoring the formation of primary and secondary oxidation products. For all of the studied GGM and GX, the content of phenolic residues ranged from 18 µg/g to 4 mg/g. The quantities of phenolic compounds in PHWE GGM and GX were higher than in TMP and BLNGGM and GX. Con GGM and GX exhibited higher amount of phenolic residues than the corresponding EtOH ones. Triterpenes were not detected which indicated their negligible contribution to emulsion stabilization. Con_TMP exhibited high iron binding capacity whereas the others exhibited average capacities. TMP GGM showed higher hydroxyl radical scavenging capacity compared to other GGM. The content of phenolic residues correlated with DPPH radical scavenging capacity for both GGM and GX: Radical scavenging capacity was greatest in samples having high number of phenolic residues. The average droplet size D[3,2] of emulsions stabilized by TMP GGM increased at a higher rate than that of stabilized by EtOH_GX. EtOH_GX was more stable due to its higher phenolic content and hydroxyl radical scavenging capacity compared to TMP GGM. Peroxide values and volatile oxidation products indicated that Con_TMP stabilized emulsion oxidized at a higher rate compared to EtOH_GX stabilized emulsion. This study showed the potential benefits to have coextracted wood extractives in hemicellulose isolates instead of removing them. Wood extractives clearly affect the stability of emulsions.